The present invention generally relates to a copying apparatus and more particularly, to a copying apparatus equipped with a brushless DC motor for driving a light source, a photosensitive or photoreceptor drum, etc. of the copying apparatus.
Conventionally, in copying apparatuses, it has been so arranged that a motor is used for scanning an original sheet to be copied or rotating a photoreceptor drum. A brushless DC motor is frequently employed as the motor. In order to scan the original sheet by using a rotational force of the motor in, for example, a copying apparatus of a type having a movable optical system, a light source is moved via an output shaft of the motor, pulleys, a wire and a fixing portion of the light source, which is attached to the wire. However, in the case where the copying apparatus has an apparatus housing split into an upper unit 1 and a lower unit 2 such that the upper unit 1 and the lower unit 2 can be retracted away from each other about a fulcrum 3 at the time of a maintenance operation of the copying apparatus or jamming of copy paper sheets as shown in FIG. 1, such a phenomenon may take place that a light source 4 is moved downwardly with the acceleration by its own weight from a start position (home position) A towards a limit position B when the upper unit 1 and the lower unit 2 have been retracted away from each other as shown in FIG. 2. At this time, if the light source 4 is allowed to move downwardly, the light source 4 proceeds beyond the limit position B into collision with a portion of the apparatus housing, thereby resulting in damage to a lamp of the light source 4 or deviation of an optical axis of the light source 4 from a predetermined position. In this case, the displacement of the light source 4 is transmitted to the output shaft of the motor through a wire 5 trained over the auxiliary pulleys 6 and 7, the auxiliary pulleys 6 and 7 and a pulley 8 which is coupled, in contact with the wire 5, with the output shaft of the motor. However, since the motor is subjected, as a force for holding the motor at a stop, to only a frictional resistance of the motor, it is impossible to prevent the displacement of the light source 4 unless another external force for holding the motor at a stop is applied to the motor. An interlocking switch 26 is provided at an interfacial portion between the upper unit 1 and the lower unit 2.
Furthermore, in a copying apparatus provided, as a photoreceptor, with a sheetlike photoreceptor 9 as shown in FIG. 3, since a joint portion 11 for retaining opposite ends of the photoreceptor 9 at an outer circumference of a drum 10 is required to confront a developing tank 12 at the time when the motor is not being actuated, forces applied to the drum 10 become non-uniform. Therefore, unless a sufficiently large force for holding a motor 13 at a stop is applied to the motor 13, the drum 10 is rotated in the clockwise direction in FIG. 3 from a position shown in FIG. 3 and thus, it becomes impossible to hold the drum 10 at the position shown in FIG. 3, at which the joint portion 11 and the developing tank 12 confront each other. Consequently, in the prior art copying apparatus of FIG. 3, it has been so arranged that a brake mechanism employing a solenoid or a brake plate is provided in the motor 13 so as to prevent rotation of the output shaft of the motor by a frictional force at the time when the motor is not being actuated. However, the known copying apparatus of FIG. 3 has such inconveniences that employment of the brake mechanism results in rise of its production cost and difficulty in making the copying apparatus compact in size.